Answered briefly

64 € as an online ticket, 72 € at the toll station, 25 € with ØresundGO — each per single crossing for vehicles up to six metres.

30 days from purchase, with no fixed date and no fixed time. You travel whenever it suits within that window.

At the toll station only in Danish or Swedish kroner — or by card. Billing is always in DKK.

The toll station sits on the Swedish side at Lernacken. In both directions you pass the same station.

Yes. Transponders from the EasyGo system are recognised; the discount, however, depends on your contract, not on the device.

First to trailers and high-sided vehicles, then completely if the wind holds. Current conditions are in the traffic section.